In automotive thermal management, coolant level in a cooling system is closely controlled for improved engine efficiency and emissions quality. The coolant may comprise a mixture of water and glycol and a chemical balance between the two components is maintained to improve the performance of the cooling system. As the coolant is circulated through engine components to control engine temperature, over time, due to evaporation, the water content of the coolant may reduce and also there may be an overall reduction in the coolant level and an increase in the coolant glycol level. Also, leakages may cause a decrease in the coolant glycol level.
Various approaches are provided for maintaining the water balance in an engine coolant system. In one example, as shown in U.S. Pat. No. 6,171,718, Murach et al. discloses a method of monitoring coolant level in a coolant reservoir inside a fuel cell used in a vehicle. If the coolant level reduces to below a threshold, the exhaust stream may be routed through a supercharger, wherein the exhaust stream is pressurized. The pressurized exhaust stream is then passed through a pressurized condensing heat exchanger and water is recovered from the pressurized exhaust stream. This recovered water may be used to restore the water level in the coolant.
However, the inventors herein have recognized potential disadvantages with the above approach. As one example, in the approach shown by Murach et al., operating parameters of the fuel cell may have to be adjusted in order to produce condensed water to be added to the coolant system. The change in the operating parameters may adversely affect the operation of the fuel cell and the associated vehicle. Also, in the aforementioned approach, the glycol level in the coolant is not taken into account while adjusting the coolant level. Due to higher coolant temperatures, a significant amount of water in the coolant may evaporate and a higher relative amount of glycol in the coolant may cause over-heating of the coolant thereby adversely affecting performance of the cooling system and the overall engine performance. Further, use of water stored in a reservoir (for coolant system maintenance) which needs to be externally refilled and maintained may add to the maintenance cost of the vehicle.
In one example, the issues described above may be addressed by an engine method comprising: in response to a relative amount of glycol in an engine coolant being higher than a threshold amount, and/or in response to an engine coolant level being lower than a threshold coolant level, supplying water from an on-board water collection system to a coolant reservoir; and in response to the relative amount of glycol in the engine coolant being lower than the threshold amount, setting a diagnostic code. In this way, by monitoring the coolant level and glycol level in a coolant and by opportunistically adding water harvested from one or more vehicle components to the coolant, water glycol balance and the coolant level may be maintained in the coolant system.
As one example, the coolant level in a coolant reservoir may be measured via a float sensor or may be estimated based on a coolant temperature sensor output data. The glycol level in the coolant may be directly measured via a glycol level sensor or estimated from the coolant level in the reservoir. If it is inferred that the relative amount of glycol in the coolant is higher than a threshold and/or if the coolant level in the reservoir is lower than a threshold, an amount of water may be added to the coolant such that the coolant level increases to the threshold level, and the relative glycol amount decreases to the threshold amount. The amount of water to be added may be based on the one or more of a difference between the current coolant level and the threshold and the difference between the actual relative glycol amount and the desired relative glycol amount. The water to be added to the coolant system may be harvested from condensate accumulated in a plurality of vehicle components. As such, a significant amount of water condenses at an evaporator of an air conditioning system and this water may be stored in a reservoir to be opportunistically used to maintain the coolant level. In addition, water may be recovered from vehicle door seal channels, exhaust system, intake system charge air cooler, fuel system, etc. Each of the on-board water recovery systems may have individual reservoirs to collect the water which may then be routed to a centralized water tank via a plurality of pumps and from thereon the water may be supplied to the coolant reservoir based on demand. In addition, the water reservoirs may be coupled to drainage lines to remove any excess water. Before adding the water to the coolant reservoir, the purity of water may also be determined and in response to a lower than threshold water quality, water stored in the tank may be drained. If it is determined that the relative glycol amount in the coolant is lower than the threshold amount, a diagnostic code may be set notifying an operator to externally supply glycol.
In this way, by sourcing water from a plurality of existing vehicle components such as the air conditioning system for use in the coolant system, engine operating conditions may not have to be altered for water recovery. Also, by internally sourcing the water, dependence on external water supply may be reduced which may also reduce the maintenance cost of externally supplying water to the coolant system. By sourcing water from a plurality of vehicle systems, burden on any one particular system may be reduced. The technical effect of estimating the glycol level and adjusting the water level in the coolant order to maintain a desired water glycol balance is that overheating and degradation of the coolant system may be reduced. Also, by assessing the water quality before adding the water to the coolant system, possibility of contamination of the coolant system caused due to excessive glycol content in coolant may be reduced. Overall, by maintaining the chemical balance in the coolant system, engine operation may be improved.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.